The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

London attack suspect: Pub fights and anti-Muslim rants

The 47-year-old man accused of driving a van into a crowd of Muslim worshippers outside a London mosque was "troubled", according to his family, while those who know him described a man who verbally abused Muslim children.

Darren Osborne, a father of four from Cardiff in Wales, was arrested after the attack near Finsbury Park Mosque early Monday and is being questioned by police on suspicion of attempted murder and terrorism.

According to witnesses who detained the man before police arrested him, he was shouting that he wanted to "kill all Muslims" before he was taken away.

Neighbours said Osborne had been thrown out of The Hollybush, his local pub in Pentwyn, a suburb of Cardiff, on Saturday for drunkenly insulting Muslims.

"He was cursing Muslims and saying he would do some damage," according to a regular at the pub quoted by The Sun.

His Muslim neighbour, Khadijeh Sherizi, said she had never had any problems with Osborne until this weekend, when he insulted her children.

Her son Nadeem, 12, was quoted in The Guardian as saying: "I was on my bike and he just came up to me and said 'inbred'."